rxrpc: Improve skb tracing

Improve sk_buff tracing within AF_RXRPC by the following means:

 (1) Use an enum to note the event type rather than plain integers and use
     an array of event names rather than a big multi ?: list.

 (2) Distinguish Rx from Tx packets and account them separately.  This
     requires the call phase to be tracked so that we know what we might
     find in rxtx_buffer[].

 (3) Add a parameter to rxrpc_{new,see,get,free}_skb() to indicate the
     event type.

 (4) A pair of 'rotate' events are added to indicate packets that are about
     to be rotated out of the Rx and Tx windows.

 (5) A pair of 'lost' events are added, along with rxrpc_lose_skb() for
     packet loss injection recording.

Signed-off-by: David Howells <dhowells@redhat.com>
 

13 files changed, 127 insertions, 55 deletions

diff --git a/net/rxrpc/af_rxrpc.c b/net/rxrpc/af_rxrpc.c
index 09f81befc705..8dbf7bed2cc4 100644
--- a/net/rxrpc/af_rxrpc.c
+++ b/net/rxrpc/af_rxrpc.c
@@ -45,7 +45,7 @@ u32 rxrpc_epoch;
 atomic_t rxrpc_debug_id;
 
 /* count of skbs currently in use */
-atomic_t rxrpc_n_skbs;
+atomic_t rxrpc_n_tx_skbs, rxrpc_n_rx_skbs;
 
 struct workqueue_struct *rxrpc_workqueue;
 
@@ -867,7 +867,8 @@ static void __exit af_rxrpc_exit(void)
 	proto_unregister(&rxrpc_proto);
 	rxrpc_destroy_all_calls();
 	rxrpc_destroy_all_connections();
-	ASSERTCMP(atomic_read(&rxrpc_n_skbs), ==, 0);
+	ASSERTCMP(atomic_read(&rxrpc_n_tx_skbs), ==, 0);
+	ASSERTCMP(atomic_read(&rxrpc_n_rx_skbs), ==, 0);
 	rxrpc_destroy_all_locals();
 
 	remove_proc_entry("rxrpc_conns", init_net.proc_net);
diff --git a/net/rxrpc/ar-internal.h b/net/rxrpc/ar-internal.h
index a17341d2df3d..034f525f2235 100644
--- a/net/rxrpc/ar-internal.h
+++ b/net/rxrpc/ar-internal.h
@@ -520,6 +520,7 @@ struct rxrpc_call {
 	rxrpc_seq_t		rx_expect_next;	/* Expected next packet sequence number */
 	u8			rx_winsize;	/* Size of Rx window */
 	u8			tx_winsize;	/* Maximum size of Tx window */
+	bool			tx_phase;	/* T if transmission phase, F if receive phase */
 	u8			nr_jumbo_bad;	/* Number of jumbo dups/exceeds-windows */
 
 	/* receive-phase ACK management */
@@ -534,6 +535,27 @@ struct rxrpc_call {
 	rxrpc_serial_t		acks_latest;	/* serial number of latest ACK received */
 };
 
+enum rxrpc_skb_trace {
+	rxrpc_skb_rx_cleaned,
+	rxrpc_skb_rx_freed,
+	rxrpc_skb_rx_got,
+	rxrpc_skb_rx_lost,
+	rxrpc_skb_rx_received,
+	rxrpc_skb_rx_rotated,
+	rxrpc_skb_rx_purged,
+	rxrpc_skb_rx_seen,
+	rxrpc_skb_tx_cleaned,
+	rxrpc_skb_tx_freed,
+	rxrpc_skb_tx_got,
+	rxrpc_skb_tx_lost,
+	rxrpc_skb_tx_new,
+	rxrpc_skb_tx_rotated,
+	rxrpc_skb_tx_seen,
+	rxrpc_skb__nr_trace
+};
+
+extern const char rxrpc_skb_traces[rxrpc_skb__nr_trace][7];
+
 enum rxrpc_conn_trace {
 	rxrpc_conn_new_client,
 	rxrpc_conn_new_service,
@@ -642,7 +664,7 @@ extern const char *rxrpc_acks(u8 reason);
 /*
  * af_rxrpc.c
  */
-extern atomic_t rxrpc_n_skbs;
+extern atomic_t rxrpc_n_tx_skbs, rxrpc_n_rx_skbs;
 extern u32 rxrpc_epoch;
 extern atomic_t rxrpc_debug_id;
 extern struct workqueue_struct *rxrpc_workqueue;
@@ -1000,10 +1022,11 @@ int rxrpc_do_sendmsg(struct rxrpc_sock *, struct msghdr *, size_t);
  */
 void rxrpc_kernel_data_consumed(struct rxrpc_call *, struct sk_buff *);
 void rxrpc_packet_destructor(struct sk_buff *);
-void rxrpc_new_skb(struct sk_buff *);
-void rxrpc_see_skb(struct sk_buff *);
-void rxrpc_get_skb(struct sk_buff *);
-void rxrpc_free_skb(struct sk_buff *);
+void rxrpc_new_skb(struct sk_buff *, enum rxrpc_skb_trace);
+void rxrpc_see_skb(struct sk_buff *, enum rxrpc_skb_trace);
+void rxrpc_get_skb(struct sk_buff *, enum rxrpc_skb_trace);
+void rxrpc_free_skb(struct sk_buff *, enum rxrpc_skb_trace);
+void rxrpc_lose_skb(struct sk_buff *, enum rxrpc_skb_trace);
 void rxrpc_purge_queue(struct sk_buff_head *);
 
 /*
diff --git a/net/rxrpc/call_event.c b/net/rxrpc/call_event.c
index f0cabc48a1b7..7d1b99824ed9 100644
--- a/net/rxrpc/call_event.c
+++ b/net/rxrpc/call_event.c
@@ -170,7 +170,7 @@ static void rxrpc_resend(struct rxrpc_call *call)
 			continue;
 
 		skb = call->rxtx_buffer[ix];
-		rxrpc_see_skb(skb);
+		rxrpc_see_skb(skb, rxrpc_skb_tx_seen);
 		sp = rxrpc_skb(skb);
 
 		if (annotation == RXRPC_TX_ANNO_UNACK) {
@@ -199,7 +199,7 @@ static void rxrpc_resend(struct rxrpc_call *call)
 			continue;
 
 		skb = call->rxtx_buffer[ix];
-		rxrpc_get_skb(skb);
+		rxrpc_get_skb(skb, rxrpc_skb_tx_got);
 		spin_unlock_bh(&call->lock);
 		sp = rxrpc_skb(skb);
 
@@ -211,7 +211,7 @@ static void rxrpc_resend(struct rxrpc_call *call)
 
 		if (rxrpc_send_data_packet(call->conn, skb) < 0) {
 			call->resend_at = now + 2;
-			rxrpc_free_skb(skb);
+			rxrpc_free_skb(skb, rxrpc_skb_tx_freed);
 			return;
 		}
 
@@ -219,7 +219,7 @@ static void rxrpc_resend(struct rxrpc_call *call)
 			rxrpc_expose_client_call(call);
 		sp->resend_at = now + rxrpc_resend_timeout;
 
-		rxrpc_free_skb(skb);
+		rxrpc_free_skb(skb, rxrpc_skb_tx_freed);
 		spin_lock_bh(&call->lock);
 
 		/* We need to clear the retransmit state, but there are two
diff --git a/net/rxrpc/call_object.c b/net/rxrpc/call_object.c
index 54f30482a7fd..f50a6094e198 100644
--- a/net/rxrpc/call_object.c
+++ b/net/rxrpc/call_object.c
@@ -182,6 +182,7 @@ static struct rxrpc_call *rxrpc_alloc_client_call(struct sockaddr_rxrpc *srx,
 		return ERR_PTR(-ENOMEM);
 	call->state = RXRPC_CALL_CLIENT_AWAIT_CONN;
 	call->service_id = srx->srx_service;
+	call->tx_phase = true;
 
 	_leave(" = %p", call);
 	return call;
@@ -458,7 +459,9 @@ void rxrpc_release_call(struct rxrpc_sock *rx, struct rxrpc_call *call)
 		rxrpc_disconnect_call(call);
 
 	for (i = 0; i < RXRPC_RXTX_BUFF_SIZE; i++) {
-		rxrpc_free_skb(call->rxtx_buffer[i]);
+		rxrpc_free_skb(call->rxtx_buffer[i],
+			       (call->tx_phase ? rxrpc_skb_tx_cleaned :
+				rxrpc_skb_rx_cleaned));
 		call->rxtx_buffer[i] = NULL;
 	}
 
@@ -552,9 +555,11 @@ void rxrpc_cleanup_call(struct rxrpc_call *call)
 
 	/* Clean up the Rx/Tx buffer */
 	for (i = 0; i < RXRPC_RXTX_BUFF_SIZE; i++)
-		rxrpc_free_skb(call->rxtx_buffer[i]);
+		rxrpc_free_skb(call->rxtx_buffer[i],
+			       (call->tx_phase ? rxrpc_skb_tx_cleaned :
+				rxrpc_skb_rx_cleaned));
 
-	rxrpc_free_skb(call->tx_pending);
+	rxrpc_free_skb(call->tx_pending, rxrpc_skb_tx_cleaned);
 
 	call_rcu(&call->rcu, rxrpc_rcu_destroy_call);
 }
diff --git a/net/rxrpc/conn_event.c b/net/rxrpc/conn_event.c
index 9b19c51831aa..75a15a4c74c3 100644
--- a/net/rxrpc/conn_event.c
+++ b/net/rxrpc/conn_event.c
@@ -388,7 +388,7 @@ void rxrpc_process_connection(struct work_struct *work)
 	/* go through the conn-level event packets, releasing the ref on this
 	 * connection that each one has when we've finished with it */
 	while ((skb = skb_dequeue(&conn->rx_queue))) {
-		rxrpc_see_skb(skb);
+		rxrpc_see_skb(skb, rxrpc_skb_rx_seen);
 		ret = rxrpc_process_event(conn, skb, &abort_code);
 		switch (ret) {
 		case -EPROTO:
@@ -399,7 +399,7 @@ void rxrpc_process_connection(struct work_struct *work)
 			goto requeue_and_leave;
 		case -ECONNABORTED:
 		default:
-			rxrpc_free_skb(skb);
+			rxrpc_free_skb(skb, rxrpc_skb_rx_freed);
 			break;
 		}
 	}
@@ -416,7 +416,7 @@ requeue_and_leave:
 protocol_error:
 	if (rxrpc_abort_connection(conn, -ret, abort_code) < 0)
 		goto requeue_and_leave;
-	rxrpc_free_skb(skb);
+	rxrpc_free_skb(skb, rxrpc_skb_rx_freed);
 	_leave(" [EPROTO]");
 	goto out;
 }
diff --git a/net/rxrpc/input.c b/net/rxrpc/input.c
index b690220533c6..84bb16d47b85 100644
--- a/net/rxrpc/input.c
+++ b/net/rxrpc/input.c
@@ -50,7 +50,7 @@ static void rxrpc_rotate_tx_window(struct rxrpc_call *call, rxrpc_seq_t to)
 		call->tx_hard_ack++;
 		ix = call->tx_hard_ack & RXRPC_RXTX_BUFF_MASK;
 		skb = call->rxtx_buffer[ix];
-		rxrpc_see_skb(skb);
+		rxrpc_see_skb(skb, rxrpc_skb_tx_rotated);
 		call->rxtx_buffer[ix] = NULL;
 		call->rxtx_annotations[ix] = 0;
 		skb->next = list;
@@ -66,7 +66,7 @@ static void rxrpc_rotate_tx_window(struct rxrpc_call *call, rxrpc_seq_t to)
 		skb = list;
 		list = skb->next;
 		skb->next = NULL;
-		rxrpc_free_skb(skb);
+		rxrpc_free_skb(skb, rxrpc_skb_tx_freed);
 	}
 }
 
@@ -99,6 +99,7 @@ static bool rxrpc_end_tx_phase(struct rxrpc_call *call, const char *abort_why)
 	default:
 		break;
 	case RXRPC_CALL_CLIENT_AWAIT_REPLY:
+		call->tx_phase = false;
 		call->state = RXRPC_CALL_CLIENT_RECV_REPLY;
 		break;
 	case RXRPC_CALL_SERVER_AWAIT_ACK:
@@ -278,7 +279,7 @@ next_subpacket:
 	 * Barriers against rxrpc_recvmsg_data() and rxrpc_rotate_rx_window()
 	 * and also rxrpc_fill_out_ack().
 	 */
-	rxrpc_get_skb(skb);
+	rxrpc_get_skb(skb, rxrpc_skb_rx_got);
 	call->rxtx_annotations[ix] = annotation;
 	smp_wmb();
 	call->rxtx_buffer[ix] = skb;
@@ -691,13 +692,13 @@ void rxrpc_data_ready(struct sock *udp_sk)
 		return;
 	}
 
-	rxrpc_new_skb(skb);
+	rxrpc_new_skb(skb, rxrpc_skb_rx_received);
 
 	_net("recv skb %p", skb);
 
 	/* we'll probably need to checksum it (didn't call sock_recvmsg) */
 	if (skb_checksum_complete(skb)) {
-		rxrpc_free_skb(skb);
+		rxrpc_free_skb(skb, rxrpc_skb_rx_freed);
 		__UDP_INC_STATS(&init_net, UDP_MIB_INERRORS, 0);
 		_leave(" [CSUM failed]");
 		return;
@@ -821,7 +822,7 @@ void rxrpc_data_ready(struct sock *udp_sk)
 discard_unlock:
 	rcu_read_unlock();
 discard:
-	rxrpc_free_skb(skb);
+	rxrpc_free_skb(skb, rxrpc_skb_rx_freed);
 out:
 	trace_rxrpc_rx_done(0, 0);
 	return;
diff --git a/net/rxrpc/local_event.c b/net/rxrpc/local_event.c
index f073e932500e..190f68bd9e27 100644
--- a/net/rxrpc/local_event.c
+++ b/net/rxrpc/local_event.c
@@ -90,7 +90,7 @@ void rxrpc_process_local_events(struct rxrpc_local *local)
 	if (skb) {
 		struct rxrpc_skb_priv *sp = rxrpc_skb(skb);
 
-		rxrpc_see_skb(skb);
+		rxrpc_see_skb(skb, rxrpc_skb_rx_seen);
 		_debug("{%d},{%u}", local->debug_id, sp->hdr.type);
 
 		switch (sp->hdr.type) {
@@ -107,7 +107,7 @@ void rxrpc_process_local_events(struct rxrpc_local *local)
 			break;
 		}
 
-		rxrpc_free_skb(skb);
+		rxrpc_free_skb(skb, rxrpc_skb_rx_freed);
 	}
 
 	_leave("");
diff --git a/net/rxrpc/misc.c b/net/rxrpc/misc.c
index c7065d893d1e..026e1f2e83ff 100644
--- a/net/rxrpc/misc.c
+++ b/net/rxrpc/misc.c
@@ -102,6 +102,24 @@ const char *rxrpc_acks(u8 reason)
 	return str[reason];
 }
 
+const char rxrpc_skb_traces[rxrpc_skb__nr_trace][7] = {
+	[rxrpc_skb_rx_cleaned]		= "Rx CLN",
+	[rxrpc_skb_rx_freed]		= "Rx FRE",
+	[rxrpc_skb_rx_got]		= "Rx GOT",
+	[rxrpc_skb_rx_lost]		= "Rx *L*",
+	[rxrpc_skb_rx_received]		= "Rx RCV",
+	[rxrpc_skb_rx_purged]		= "Rx PUR",
+	[rxrpc_skb_rx_rotated]		= "Rx ROT",
+	[rxrpc_skb_rx_seen]		= "Rx SEE",
+	[rxrpc_skb_tx_cleaned]		= "Tx CLN",
+	[rxrpc_skb_tx_freed]		= "Tx FRE",
+	[rxrpc_skb_tx_got]		= "Tx GOT",
+	[rxrpc_skb_tx_lost]		= "Tx *L*",
+	[rxrpc_skb_tx_new]		= "Tx NEW",
+	[rxrpc_skb_tx_rotated]		= "Tx ROT",
+	[rxrpc_skb_tx_seen]		= "Tx SEE",
+};
+
 const char rxrpc_conn_traces[rxrpc_conn__nr_trace][4] = {
 	[rxrpc_conn_new_client]		= "NWc",
 	[rxrpc_conn_new_service]	= "NWs",
diff --git a/net/rxrpc/output.c b/net/rxrpc/output.c
index 2c9daeadce87..a2cad5ce7416 100644
--- a/net/rxrpc/output.c
+++ b/net/rxrpc/output.c
@@ -324,7 +324,7 @@ void rxrpc_reject_packets(struct rxrpc_local *local)
 	whdr.type = RXRPC_PACKET_TYPE_ABORT;
 
 	while ((skb = skb_dequeue(&local->reject_queue))) {
-		rxrpc_see_skb(skb);
+		rxrpc_see_skb(skb, rxrpc_skb_rx_seen);
 		sp = rxrpc_skb(skb);
 
 		if (rxrpc_extract_addr_from_skb(&srx, skb) == 0) {
@@ -343,7 +343,7 @@ void rxrpc_reject_packets(struct rxrpc_local *local)
 			kernel_sendmsg(local->socket, &msg, iov, 2, size);
 		}
 
-		rxrpc_free_skb(skb);
+		rxrpc_free_skb(skb, rxrpc_skb_rx_freed);
 	}
 
 	_leave("");
diff --git a/net/rxrpc/peer_event.c b/net/rxrpc/peer_event.c
index 9e0725f5652b..18276e7cb9e0 100644
--- a/net/rxrpc/peer_event.c
+++ b/net/rxrpc/peer_event.c
@@ -155,11 +155,11 @@ void rxrpc_error_report(struct sock *sk)
 		_leave("UDP socket errqueue empty");
 		return;
 	}
-	rxrpc_new_skb(skb);
+	rxrpc_new_skb(skb, rxrpc_skb_rx_received);
 	serr = SKB_EXT_ERR(skb);
 	if (!skb->len && serr->ee.ee_origin == SO_EE_ORIGIN_TIMESTAMPING) {
 		_leave("UDP empty message");
-		rxrpc_free_skb(skb);
+		rxrpc_free_skb(skb, rxrpc_skb_rx_freed);
 		return;
 	}
 
@@ -169,7 +169,7 @@ void rxrpc_error_report(struct sock *sk)
 		peer = NULL;
 	if (!peer) {
 		rcu_read_unlock();
-		rxrpc_free_skb(skb);
+		rxrpc_free_skb(skb, rxrpc_skb_rx_freed);
 		_leave(" [no peer]");
 		return;
 	}
@@ -179,7 +179,7 @@ void rxrpc_error_report(struct sock *sk)
 	     serr->ee.ee_code == ICMP_FRAG_NEEDED)) {
 		rxrpc_adjust_mtu(peer, serr);
 		rcu_read_unlock();
-		rxrpc_free_skb(skb);
+		rxrpc_free_skb(skb, rxrpc_skb_rx_freed);
 		rxrpc_put_peer(peer);
 		_leave(" [MTU update]");
 		return;
@@ -187,7 +187,7 @@ void rxrpc_error_report(struct sock *sk)
 
 	rxrpc_store_error(peer, serr);
 	rcu_read_unlock();
-	rxrpc_free_skb(skb);
+	rxrpc_free_skb(skb, rxrpc_skb_rx_freed);
 
 	/* The ref we obtained is passed off to the work item */
 	rxrpc_queue_work(&peer->error_distributor);
diff --git a/net/rxrpc/recvmsg.c b/net/rxrpc/recvmsg.c
index 79e65668bc58..6ba4af5a8d95 100644
--- a/net/rxrpc/recvmsg.c
+++ b/net/rxrpc/recvmsg.c
@@ -155,6 +155,7 @@ static void rxrpc_end_rx_phase(struct rxrpc_call *call)
 		break;
 
 	case RXRPC_CALL_SERVER_RECV_REQUEST:
+		call->tx_phase = true;
 		call->state = RXRPC_CALL_SERVER_ACK_REQUEST;
 		break;
 	default:
@@ -185,7 +186,7 @@ static void rxrpc_rotate_rx_window(struct rxrpc_call *call)
 	hard_ack++;
 	ix = hard_ack & RXRPC_RXTX_BUFF_MASK;
 	skb = call->rxtx_buffer[ix];
-	rxrpc_see_skb(skb);
+	rxrpc_see_skb(skb, rxrpc_skb_rx_rotated);
 	sp = rxrpc_skb(skb);
 	flags = sp->hdr.flags;
 	serial = sp->hdr.serial;
@@ -197,7 +198,7 @@ static void rxrpc_rotate_rx_window(struct rxrpc_call *call)
 	/* Barrier against rxrpc_input_data(). */
 	smp_store_release(&call->rx_hard_ack, hard_ack);
 
-	rxrpc_free_skb(skb);
+	rxrpc_free_skb(skb, rxrpc_skb_rx_freed);
 
 	_debug("%u,%u,%02x", hard_ack, top, flags);
 	trace_rxrpc_receive(call, rxrpc_receive_rotate, serial, hard_ack);
@@ -317,7 +318,7 @@ static int rxrpc_recvmsg_data(struct socket *sock, struct rxrpc_call *call,
 			break;
 		}
 		smp_rmb();
-		rxrpc_see_skb(skb);
+		rxrpc_see_skb(skb, rxrpc_skb_rx_seen);
 		sp = rxrpc_skb(skb);
 
 		if (!(flags & MSG_PEEK))
diff --git a/net/rxrpc/sendmsg.c b/net/rxrpc/sendmsg.c
index 28d8f73cf11d..6a39ee97a0b7 100644
--- a/net/rxrpc/sendmsg.c
+++ b/net/rxrpc/sendmsg.c
@@ -100,7 +100,7 @@ static void rxrpc_queue_packet(struct rxrpc_call *call, struct sk_buff *skb,
 	ASSERTCMP(seq, ==, call->tx_top + 1);
 
 	ix = seq & RXRPC_RXTX_BUFF_MASK;
-	rxrpc_get_skb(skb);
+	rxrpc_get_skb(skb, rxrpc_skb_tx_got);
 	call->rxtx_annotations[ix] = RXRPC_TX_ANNO_UNACK;
 	smp_wmb();
 	call->rxtx_buffer[ix] = skb;
@@ -146,7 +146,7 @@ static void rxrpc_queue_packet(struct rxrpc_call *call, struct sk_buff *skb,
 		rxrpc_instant_resend(call, ix);
 	}
 
-	rxrpc_free_skb(skb);
+	rxrpc_free_skb(skb, rxrpc_skb_tx_freed);
 	_leave("");
 }
 
@@ -201,7 +201,7 @@ static int rxrpc_send_data(struct rxrpc_sock *rx,
 
 	skb = call->tx_pending;
 	call->tx_pending = NULL;
-	rxrpc_see_skb(skb);
+	rxrpc_see_skb(skb, rxrpc_skb_tx_seen);
 
 	copied = 0;
 	do {
@@ -242,7 +242,7 @@ static int rxrpc_send_data(struct rxrpc_sock *rx,
 			if (!skb)
 				goto maybe_error;
 
-			rxrpc_new_skb(skb);
+			rxrpc_new_skb(skb, rxrpc_skb_tx_new);
 
 			_debug("ALLOC SEND %p", skb);
 
@@ -352,7 +352,7 @@ out:
 	return ret;
 
 call_terminated:
-	rxrpc_free_skb(skb);
+	rxrpc_free_skb(skb, rxrpc_skb_tx_freed);
 	_leave(" = %d", -call->error);
 	return -call->error;
 
diff --git a/net/rxrpc/skbuff.c b/net/rxrpc/skbuff.c
index 620d9ccaf3c1..5154cbf7e540 100644
--- a/net/rxrpc/skbuff.c
+++ b/net/rxrpc/skbuff.c
@@ -18,55 +18,77 @@
 #include <net/af_rxrpc.h>
 #include "ar-internal.h"
 
+#define select_skb_count(op) (op >= rxrpc_skb_tx_cleaned ? &rxrpc_n_tx_skbs : &rxrpc_n_rx_skbs)
+
 /*
- * Note the existence of a new-to-us socket buffer (allocated or dequeued).
+ * Note the allocation or reception of a socket buffer.
  */
-void rxrpc_new_skb(struct sk_buff *skb)
+void rxrpc_new_skb(struct sk_buff *skb, enum rxrpc_skb_trace op)
 {
 	const void *here = __builtin_return_address(0);
-	int n = atomic_inc_return(&rxrpc_n_skbs);
-	trace_rxrpc_skb(skb, 0, atomic_read(&skb->users), n, here);
+	int n = atomic_inc_return(select_skb_count(op));
+	trace_rxrpc_skb(skb, op, atomic_read(&skb->users), n, here);
 }
 
 /*
  * Note the re-emergence of a socket buffer from a queue or buffer.
  */
-void rxrpc_see_skb(struct sk_buff *skb)
+void rxrpc_see_skb(struct sk_buff *skb, enum rxrpc_skb_trace op)
 {
 	const void *here = __builtin_return_address(0);
 	if (skb) {
-		int n = atomic_read(&rxrpc_n_skbs);
-		trace_rxrpc_skb(skb, 1, atomic_read(&skb->users), n, here);
+		int n = atomic_read(select_skb_count(op));
+		trace_rxrpc_skb(skb, op, atomic_read(&skb->users), n, here);
 	}
 }
 
 /*
  * Note the addition of a ref on a socket buffer.
  */
-void rxrpc_get_skb(struct sk_buff *skb)
+void rxrpc_get_skb(struct sk_buff *skb, enum rxrpc_skb_trace op)
 {
 	const void *here = __builtin_return_address(0);
-	int n = atomic_inc_return(&rxrpc_n_skbs);
-	trace_rxrpc_skb(skb, 2, atomic_read(&skb->users), n, here);
+	int n = atomic_inc_return(select_skb_count(op));
+	trace_rxrpc_skb(skb, op, atomic_read(&skb->users), n, here);
 	skb_get(skb);
 }
 
 /*
  * Note the destruction of a socket buffer.
  */
-void rxrpc_free_skb(struct sk_buff *skb)
+void rxrpc_free_skb(struct sk_buff *skb, enum rxrpc_skb_trace op)
 {
 	const void *here = __builtin_return_address(0);
 	if (skb) {
 		int n;
 		CHECK_SLAB_OKAY(&skb->users);
-		n = atomic_dec_return(&rxrpc_n_skbs);
-		trace_rxrpc_skb(skb, 3, atomic_read(&skb->users), n, here);
+		n = atomic_dec_return(select_skb_count(op));
+		trace_rxrpc_skb(skb, op, atomic_read(&skb->users), n, here);
 		kfree_skb(skb);
 	}
 }
 
 /*
+ * Note the injected loss of a socket buffer.
+ */
+void rxrpc_lose_skb(struct sk_buff *skb, enum rxrpc_skb_trace op)
+{
+	const void *here = __builtin_return_address(0);
+	if (skb) {
+		int n;
+		CHECK_SLAB_OKAY(&skb->users);
+		if (op == rxrpc_skb_tx_lost) {
+			n = atomic_read(select_skb_count(op));
+			trace_rxrpc_skb(skb, op, atomic_read(&skb->users), n, here);
+		} else {
+			n = atomic_dec_return(select_skb_count(op));
+			trace_rxrpc_skb(skb, op, atomic_read(&skb->users), n, here);
+			kfree_skb(skb);
+		}
+	}
+}
+
+/*
  * Clear a queue of socket buffers.
  */
 void rxrpc_purge_queue(struct sk_buff_head *list)
@@ -74,8 +96,9 @@ void rxrpc_purge_queue(struct sk_buff_head *list)
 	const void *here = __builtin_return_address(0);
 	struct sk_buff *skb;
 	while ((skb = skb_dequeue((list))) != NULL) {
-		int n = atomic_dec_return(&rxrpc_n_skbs);
-		trace_rxrpc_skb(skb, 4, atomic_read(&skb->users), n, here);
+		int n = atomic_dec_return(select_skb_count(rxrpc_skb_rx_purged));
+		trace_rxrpc_skb(skb, rxrpc_skb_rx_purged,
+				atomic_read(&skb->users), n, here);
 		kfree_skb(skb);
 	}
 }